Dual activation of AhR and Nrf2 pathways by the natural stilbenoid tapinarof protects against particulate matter-induced skin barrier dysfunction

Abstract

Particulate matter (PM) causes skin barrier dysfunction by inducing reactive oxygen species (ROS) overproduction and oxidative stress. The aryl hydrocarbon receptor (AhR) and nuclear factor erythroid 2-related factor (Nrf2) coordinate xenobiotic metabolism and antioxidant defense, respectively, playing key roles in cytoprotection. This study aimed to investigate the therapeutic potential of tapinarof, a natural stilbenoid dually activating AhR and Nrf2 pathways, against PM-induced epidermal damage. Human keratinocyte HaCaT cells were exposed to urban dust PM (NIST® SRM® 1649b) to model PM-induced epidermal damage. An image-based analysis algorithm that eliminates PM fluorescence interference was developed, prompting the use of alternative wavelengths for specifically analyzing PM-induced cellular responses. Tapinarof potentiated PM-induced CYP1A1 and HO-1 expression, confirming AhR/Nrf2 activation. This dual pathway activation protected cells from PM-induced oxidative stress and cell death, as validated using the AhR antagonist, CH223191, and Nrf2 inhibitor, brusatol. Confocal imaging and immunoblotting suggested that tapinarof preserved PM-damaged epidermal barrier integrity by restoring the delocalization of tight junction protein ZO-1 and adherens junction complex E-cadherin/β-catenin and maintaining expressions of cornified envelope protein filaggrin. Dual activation of AhR/Nrf2 pathways effectively protects against PM-induced epidermal barrier dysfunction, highlighting the therapeutic potential of naturally derived dual AhR/Nrf2 activators like tapinarof against environmental skin damage.